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Updated: May 19, 2026

18F-Labeling of Radiotracers Functionalized with a Silicon Fluoride Acceptor (SiFA) for Positron Emission Tomography
Published on: January 11, 2020
Electrophilic addition of chlorine monofluoride for PET tracers
Anna Kirjavainen1, Sarita Forsback, Tove J Grönroos
1Radiopharmaceutical Chemistry Laboratory, Turku PET Centre, University of Turku, Turku, Finland.
Purpose:
We have studied the utility of [(18)F]ClF electrophilic addition to the carbon-carbon double bond of analogues of a model positron emission tomography (PET) tracer, [(18)F]EF5. The consequence of simultaneous chlorine/fluorine addition on lipophilicity and biological activity of the molecule is evaluated.
Procedures:
Post-target produced [(18)F]F2 was reacted with Cl2 to produce [(18)F]ClF, which was used in electrophilic addition.
Results:
[(18)F]ClF was produced and used to label chlorinated analogues of [(18)F]EF5. The chlorinated analogues, [(18)F]EF4Cla and [(18)F]EF4Clb, were synthesized simultaneously. The in vivo uptake of the analogues compared well with [(18)F]EF5 uptake in tumor-bearing mice.
Conclusion:
[(18)F]ClF is a suitable labeling reagent for electrophilic addition to double bonds of PET tracers. The results show that the modification of the pentafluoro group of [(18)F]EF5 by monofluorine-for-chlorine exchange affected the lipophilicity, but the hypoxia avidity of these molecules was not apparently altered.
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